Additive manufacturing apparatus and additive manufacturing method

Abstract

The invention provides additive manufacturing equipment and an additive manufacturing method. The additive manufacturing equipment comprises a cylinder body, a lifting table, a spraying assembly, a heating assembly and an electromagnetic induction coil. Wherein the cylinder body is used for containing liquid metal; the lifting platform is positioned in the cylinder body; the lifting table comprises a supporting plate, and the supporting plate of the lifting table can move up and down in the cylinder body; the spraying assembly is located on the side, away from the bottom of the cylinder body, of a supporting plate of the lifting table and used for spraying a printing material to the supporting plate of the lifting table and enabling the printing material to deposit layer by layer through a high-energy beam heat source to form a printing workpiece, and the formed part of the printing workpiece can be driven by the lifting table to be immersed in liquid metal. The heating assembly is located on at least one side of the cylinder body and used for heating liquid metal. The electromagnetic induction coil is arranged around the side wall of the cylinder body and used for heating and driving the liquid metal to flow when powered on. And the problem of cracking or deformation of an additive manufacturing workpiece can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of additive manufacturing, in particular to an additive manufacturing device and an additive manufacturing method. BACKGROUND

[0002] As a kind of layer-by-layer accumulation / printing manufacturing method, additive manufacturing has realized the batch production of complex structure metal / ceramic / metal matrix composite workpieces in industry, however, the temperature gradient and volume shrinkage during cooling caused by the inherent melting / solidification behavior of this technology can introduce a large amount of residual stress, which is easy to cause the deformation or cracking of the prepared workpiece, and seriously affects the additive manufacturing application and the performance, printing precision and service life of the prepared workpiece.

[0003] Chinese patents CN110523977A and CN110539386A disclose an additive manufacturing method assisted by high-temperature liquid for soaking the formed parts to relieve the residual stress problem caused by high temperature gradient, but it is found in actual implementation process that the metal or non-metal as medium is heated slowly in the form of heat diffusion and the temperature distribution is uneven; the cooling rate after printing is difficult to control, and in-situ heat treatment cannot be realized. The above factors limit the practical production application of high-temperature liquid assisted additive manufacturing. SUMMARY

[0004] The embodiment of the present application provides an additive manufacturing device, which comprises: a cylinder for containing liquid metal; a lifting platform located in the cylinder; the lifting platform comprises a support plate, and the support plate of the lifting platform can move up and down in the cylinder; a spraying assembly located on the side of the support plate of the lifting platform away from the bottom of the cylinder, for spraying printing material onto the support plate of the lifting platform and making the printing material deposit layer by layer to form a printed workpiece by a high-energy beam heat source, and the formed part of the printed workpiece can be immersed into the liquid metal by the lifting platform; a heating assembly located on at least one side of the cylinder for heating the liquid metal; an electromagnetic induction coil arranged around the side wall of the cylinder for heating and driving the liquid metal to flow when energized.

[0005] In some embodiments, there is a gap between the electromagnetic induction coil and the side wall of the cylinder.

[0006] In some embodiments, the support plate comprises a first support plate and a second support plate located on the side of the first support plate away from the bottom of the cylinder, and the second support plate is detachably connected with the first support plate.

[0007] In some embodiments, the heating assembly includes a first heating assembly disposed around the sidewall of the cylinder body in a direction from the bottom of the cylinder body to the top of the cylinder body, wherein the first heating assembly and the electromagnetic induction coil are alternately disposed around the sidewall of the cylinder body.

[0008] In some embodiments, the additive manufacturing apparatus further includes a temperature sensing element and a controller, the controller being electrically connected to the temperature sensing element and the heating assembly, the temperature sensing element being used to detect the temperature of the liquid metal, and the controller being used to collect the temperature detected by the temperature sensing element and control the heating assembly to stop heating or maintain the target temperature when the temperature of the liquid metal reaches the target temperature.

[0009] In some embodiments, the temperature sensing element includes a first temperature sensing element disposed on the inner wall of the cylinder and in contact with the liquid metal; And / or, the temperature sensing element includes a second temperature sensing element, the lifting platform includes a lifting shaft connected to the support plate, the lifting shaft has a hollow cavity, and the second temperature sensing element is located in the hollow cavity and in contact with the support plate.

[0010] In some embodiments, the additive manufacturing apparatus further includes an insulation layer disposed on the side of the heating assembly away from the cylinder.

[0011] In some embodiments, the additive manufacturing apparatus further includes a cooling assembly located on the outer surface of the cylinder and in contact with the cylinder.

[0012] In some embodiments, the heating assembly further includes a second heating assembly, and both the second heating assembly and the cooling assembly are located on the bottom wall of the cylinder away from the lifting platform, and the second heating assembly and the cooling assembly are arranged alternately.

[0013] This application also provides an additive manufacturing method, based on the aforementioned additive manufacturing equipment, the additive manufacturing method comprising: The metal inside the cylinder is heated and melted into a liquid state, and the temperature of the liquid metal is maintained within a preset temperature range; The electromagnetic induction coil is controlled to keep the liquid metal in a heated and convection state under the electromagnetic force of the coil. The printing material is sprayed onto the support plate of the lifting platform, and the printing material is deposited layer by layer to form a printed workpiece through a high-energy beam heat source. The lifting platform is controlled to move closer to the bottom of the cylinder and move down, and the formed part of the printed workpiece is immersed in the liquid metal. After printing is completed, the printed workpiece is completely immersed in liquid metal for in-situ heat treatment. The temperature of the liquid metal is cooled to slightly above the melting point of the liquid metal, and the cooling rate is adjusted as needed by at least one of the heating components, electromagnetic induction coils, insulation layers and cooling components; The control lift is moved up until the upper surface of the lift is exposed outside the liquid metal.

[0014] In some embodiments, the step of immersing the printed workpiece completely in liquid metal for in-situ heat treatment after printing is completed includes: immersing the printed workpiece completely in liquid metal after printing is completed, and maintaining the temperature of the liquid metal above the phase transition temperature or ductile-brittle transition temperature of the printed material for a preset time.

[0015] The beneficial effects of this application include: In this embodiment, because an electromagnetic induction coil is provided around the cylinder in the additive manufacturing equipment, when an alternating current is applied to the electromagnetic induction coil, a changing magnetic field is generated. According to Faraday's law of electromagnetic induction, the changing magnetic field induces eddy currents inside the liquid metal and interacts with the magnetic field generated by the electromagnetic induction coil, thereby generating a Lorentz force. Under the action of the Lorentz force, the liquid metal will generate vortex motion or convection motion. Therefore, when the formed part of the printed workpiece is immersed in the liquid metal, the electromagnetic induction coil can accelerate the flow of the liquid metal, thereby improving the uniformity and rate of heating of the formed part of the printed workpiece by the liquid metal, and avoiding uneven preheating of the printed workpiece by the liquid metal during the printing process. In addition, when the electromagnetic induction coil is energized, the eddy currents induced inside the liquid metal will also generate Joule heating, further increasing the heating rate of the liquid metal.

[0016] Additional aspects and advantages of this application will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of this application. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0018] Figure 1 The diagram shown is a structural schematic of the additive manufacturing equipment provided in an exemplary embodiment of this application; Figure 2 As shown Figure 1 A three-dimensional view of a portion of the additive manufacturing equipment shown; Figures 3-6 The diagram shown is a structural schematic of several additive manufacturing equipment provided in the exemplary embodiments of this application.

[0019] In the diagram: 10-Cylinder; 100-Printed workpiece; 20-Liquid metal; 30-Lifting platform; 30a-Hollow cavity; 31-Support plate; 311-First support plate; 311a-First through hole; 312-Second support plate; 312a-Second through hole; 32-Lifting shaft; 33-First fastener; 34-Second fastener; 40-Spraying assembly; 41-High-energy beam heat source supply structure; 411-High-energy beam heat source; 42-Material conveying structure; 421-Printing material; 50-Heating assembly; 51-First heating assembly; 52-Second heating assembly; 60-Electromagnetic induction coil; 70-Temperature detection element; 80-Controller; 91-Insulation layer; 92-Cooling assembly; 921-Cooling plate; 922-Cooling pipe. Detailed Implementation

[0020] The present application will be described more fully below with reference to the accompanying drawings in which embodiments are illustrated.

[0021] While terms such as "first," "second," etc., can be used to describe various components, such components are not limited by these terms. These terms are only used to distinguish one component from another and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more. Where there is no conflict, the features in the embodiments described below in this application may complement or combine with each other.

[0022] In the accompanying drawings, the dimensions and thicknesses of the elements may be enlarged for better understanding, clarity, and ease of description. However, this application is not limited to the dimensions and thicknesses shown in the drawings. The thicknesses of layers, films, panels, areas, and other elements may be exaggerated in the drawings for clarity. Example embodiments are shown in the drawings, wherein the same reference numerals denote the same elements.

[0023] like Figure 1 and Figure 2As shown, this application provides an additive manufacturing apparatus, including a cylinder 10, a lifting platform 30, a jetting assembly 40, a heating assembly 50, and an electromagnetic induction coil 60. The cylinder 10 is used to hold liquid metal 20; the lifting platform 30 is located inside the cylinder 10; the lifting platform 30 includes a support plate 31, which can move up and down within the cylinder 10; the jetting assembly 40 is located on the side of the support plate 31 of the lifting platform 30 away from the bottom of the cylinder 10, and is used to jet printing material 421 onto the support plate 31 of the lifting platform 30, and to deposit the printing material layer by layer through a high-energy beam heat source 411 to form a printed workpiece 100, the formed portion of the printed workpiece 100 can be immersed in the liquid metal 20 by the lifting platform 30; the heating assembly 50 is located on at least one side of the cylinder 10, and is used to heat the liquid metal 20; the electromagnetic induction coil 60 is arranged around the side wall of the cylinder 10, and is used to rapidly heat and drive the liquid metal 20 to flow when energized.

[0024] In this embodiment, since an electromagnetic induction coil 60 is provided around the cylinder 10 in the additive manufacturing equipment, when alternating current is applied to the electromagnetic induction coil 60, a changing magnetic field is generated. According to Faraday's law of electromagnetic induction, the changing magnetic field induces eddy currents inside the liquid metal 20 and interacts with the magnetic field generated by the electromagnetic induction coil 60, thereby generating a Lorentz force. Under the action of the Lorentz force, the liquid metal 20 will generate vortex motion or convection motion. Therefore, when the formed part of the printed workpiece 100 is immersed in the liquid metal 20, the electromagnetic induction coil 60 can accelerate the flow of the liquid metal 20, thereby improving the uniformity and heating rate of the liquid metal 20 on the formed part of the printed workpiece 100, and avoiding uneven preheating of the printed workpiece 100 by the liquid metal 20 during the printing process. In addition, when the electromagnetic induction coil 60 is energized, the eddy currents induced inside the liquid metal 20 will also generate Joule heating, further increasing the heating rate of the liquid metal 20.

[0025] In some embodiments, such as Figure 3 As shown, the support plate 31 includes a first support plate 311 and a second support plate 312 located on the side of the first support plate 311 away from the bottom of the cylinder 10. The second support plate 312 is detachably connected to the first support plate 311. With this configuration, during the printing process, printing material can be sprayed onto the second support plate 312. After printing, the printed workpiece can be separated from the lifting platform by removing the second support plate 312 from the first support plate 311, facilitating flexible fixing and removal of the printed workpiece and improving production efficiency.

[0026] In some embodiments, the first support plate 311 may be made of metal, such as stainless steel. The second support plate 312 may be made of metal, such as steel, titanium alloy, nickel-based high-temperature alloy, or aluminum alloy. The first support plate 311 and the second support plate 312 may be made of the same or different materials.

[0027] In some embodiments, the first support plate 311 has a first through hole 311a, the second support plate 312 has a second through hole 312a, and the lifting platform further includes a first fastener 33 and a second fastener 34. The first fastener 33 passes through the first through hole 311a and the second through hole 312a and is fixed between itself and the second fastener 34. In some embodiments, the first fastener 33 may be a screw, bolt, or bolt. In some embodiments, the second fastener may be a nut, a rivet, or a clip.

[0028] In some embodiments, the cylinder body 10 may be made of (stainless) steel, aluminum, chromium, cobalt, titanium, tantalum, or alloys thereof. In other embodiments, the inner wall of the cylinder body is coated with an alloy or ceramic coating by methods such as electroplating, spraying, cladding, or vapor deposition to improve the heat resistance and corrosion resistance of the cylinder body and extend its service life.

[0029] In some embodiments, the melting point of the liquid metal 20 is lower than the solidus temperature of the printed workpiece 100, and the boiling point of the liquid metal 20 is higher than the heating temperature required for the printed workpiece 100 (depending on the specific material of the printed workpiece 100) and the melting point of the printed workpiece 100 material (e.g., 2000℃ ± 1500℃). It should be noted that the solidus temperature of the printed workpiece 100 is the melting temperature of a portion of the low-melting-point phase of the printed workpiece 100, and is typically slightly lower than the melting point of the printed workpiece 100. In some examples, the liquid metal 20 can be at least one of elements and alloys such as gallium, indium, tin, bismuth, and lead.

[0030] In some embodiments, the electromagnetic induction coil 60 is wound with a hollow metal tube, and a cooling medium can be introduced into the hollow metal tube.

[0031] In some embodiments, the jetting assembly 40 may be a Directed Energy Deposition (DED) printing assembly, a Powder Bed Fusion (PBF) printing assembly, or a Binder Jetting (BJ) printing assembly. In one example, the jetting assembly 40 may be a Directed Energy Deposition (DED) printing assembly, for example, including a high-energy beam heat source supply structure 41 and a material delivery structure 42, wherein the high-energy beam heat source supply structure 41 is used to provide a high-energy beam heat source 411, and the material delivery structure 42 is used to deliver printing material 421 onto the support plate 31.

[0032] In some embodiments, the heating assembly 50 may include a plurality of heating elements. The heating elements may be made of ceramic, mica, ceramic fiber, metal, carbon fiber, or quartz.

[0033] In some embodiments, there is a gap between the electromagnetic induction coil 60 and the side wall of the cylinder 10. This arrangement prevents short circuits or arcing caused by contact between the electromagnetic induction coil 60 and the cylinder 10, which could damage the equipment, when the cylinder 10 is made of metal.

[0034] In some embodiments, such as Figure 1 As shown, the distance d between the electromagnetic induction coil 60 and the side wall of the cylinder 10 ranges from 1 to 10 mm. This arrangement serves two purposes: firstly, it prevents the electromagnetic induction coil 60 from being too close to the cylinder 10, which could lead to contact and short circuits in the electromagnetic induction coil 60, potentially damaging the equipment. Secondly, it prevents the electromagnetic induction coil 60 from being too far from the cylinder 10, which could reduce the magnetic field coupling efficiency, thus decreasing the flow rate or heating efficiency of the liquid metal 20, or cause uneven magnetic flux density distribution, resulting in an excessive temperature gradient and uneven heating or distribution of the liquid metal 20.

[0035] In some embodiments, the heating assembly 50 includes a first heating assembly 51, which is disposed around the sidewall of the cylinder 10. The first heating assembly 51 and the electromagnetic induction coil 60 are alternately disposed around the sidewall of the cylinder 10 in a direction from the bottom to the top of the cylinder 10. This arrangement ensures that the first heating assemblies 51 distributed evenly on the sidewall of the cylinder 10, resulting in more uniform heating across all areas of the cylinder 10. Furthermore, the spaced distribution of the electromagnetic induction coils 60 ensures that the Lorentz force exerted by the electromagnetic induction coils on the liquid metal 20 within the cylinder 10 is distributed as evenly as possible. Compared to sequentially stacking the heating assembly 50 and the electromagnetic induction coil 60 around the sidewall of the cylinder 10, this reduces the overall space occupied by the device and prevents the heating assembly 50 from burning out due to excessively close proximity between it and the electromagnetic induction coil 60.

[0036] In some embodiments, the electromagnetic induction coil 60 may have one or more turns. The heating component 50 may also have one or more, and this embodiment does not specifically limit this.

[0037] In some embodiments, the heating assembly 50 includes a plurality of heating elements distributed on the sidewall of the cylinder 10. Heating elements located adjacent to each other in the same area can be controlled by one or more switches to control the heating power. For example, a plurality of heating elements located above the electromagnetic induction coil can be controlled by one or more switches, and a plurality of heating elements located below the electromagnetic induction coil can be controlled by one or more switches. The multi-turn electromagnetic induction coil 60 is similarly controlled.

[0038] In some embodiments, the additive manufacturing equipment further includes a temperature sensing element 70 and a controller 80. The controller 80 is electrically connected to the temperature sensing element 70 and the heating assembly 50. The temperature sensing element 70 is used to detect the temperature of the liquid metal 20, and the controller 80 is used to collect the temperature detected by the temperature sensing element 70 and control the heating assembly 50 to stop heating or maintain the target temperature when the temperature of the liquid metal 20 reaches the target temperature. With this configuration, the temperature of the liquid metal 20 can be controlled in conjunction with the temperature sensing element 70 and the controller 80 to keep it within the target temperature range, thereby continuously providing the required heat to the printed workpiece 100 and avoiding uneven temperature distribution of the liquid metal 20 during the process.

[0039] In some embodiments, the temperature sensing element 70 may be a temperature sensor.

[0040] In some embodiments, such as Figure 1 As shown, the temperature sensing element 70 includes a first temperature sensing element 71, which is disposed on the inner wall of the cylinder 10 and in contact with the liquid metal 20. With this configuration, the first temperature sensing element 71 can directly acquire the temperature of the liquid metal 20, and control the temperature change of the liquid metal 20 to control the temperature change of the surrounding area of ​​the printed workpiece 100.

[0041] In some embodiments, such as Figure 1 As shown, the temperature sensing element 70 includes a second temperature sensing element 72, and the lifting platform 30 includes a lifting shaft 32 connected to the support plate 31. The lifting shaft 32 has a hollow cavity 30a, and the second temperature sensing element 72 is located inside the hollow cavity 30a and in contact with the support plate 31. This arrangement avoids long-term direct contact between the temperature sensing element 70 and the liquid metal 20, preventing heat damage to the temperature sensing element 70. Furthermore, since the support plate 31 is in direct contact with the printed workpiece 100, the temperature detected by the second temperature sensing element 72 is closer to the actual temperature of the printed workpiece 100. Therefore, when adjusting the temperature of the liquid metal 20 through the second temperature sensing element 72, the adjustment result is more accurate. It should be noted that the first temperature sensing element 71 and the second temperature sensing element 72 can be set simultaneously, or only one of them can be set.

[0042] In some embodiments, such as Figure 4 As shown, the additive manufacturing equipment also includes an insulation layer 91, which is disposed on the side of the heating assembly 50 away from the cylinder 10. This arrangement allows the insulation layer 91 to insulate the cylinder 10, reducing heat loss, improving thermal efficiency, and saving thermal energy. In some examples, the insulation layer 91 can be made of ceramic fibers (e.g., alumina-aluminosilicate fiber cotton / blanket), aerogel, or microporous insulation materials.

[0043] In some embodiments, the insulation layer 91 covers at least one of the sidewalls and bottom wall of the cylinder body 10.

[0044] In some embodiments, such as Figure 5 or Figure 6 As shown, the additive manufacturing equipment also includes a cooling component 92, which is located on the outer surface of the cylinder 10 and in contact with the cylinder 10. With this configuration, when the printed workpiece 100 is completed and the liquid metal 20 needs to be cooled before the printed workpiece 100 is removed, the cooling component 92 can be used to actively cool the liquid metal 20 to adjust the cooling rate, improve manufacturing efficiency, or meet heat treatment requirements.

[0045] In some embodiments, the heating assembly 50 further includes a second heating assembly 52. ​​Both the second heating assembly 52 and the cooling assembly 92 are located on the bottom wall of the cylinder 10 away from the lifting platform 30, and are arranged alternately. This arrangement, compared to the cooling assembly 92 and the heating assembly 50 being sequentially stacked on the outside of the cylinder 10, ensures that the cooling assembly 92 is distributed as evenly as possible at the bottom of the cylinder 10, while minimizing the overall space occupied by the additive manufacturing equipment and improving the spatial integration of the equipment.

[0046] In some embodiments, such as Figure 5 As shown, the cooling assembly 92 includes a cooling fin 921. The cooling fin 921 is in contact with the bottom of the cylinder 10. In some embodiments, the cooling fin 921 may be made of a metal such as aluminum, copper, or an alloy thereof.

[0047] In other embodiments, such as Figure 6 As shown, the cooling assembly 92 includes a cooling conduit 922. The cooling conduit 922 is used to introduce a cooling medium. The cooling medium can be a gas, a liquid, or a solid-liquid mixture.

[0048] Based on the same inventive concept, this application also provides an additive manufacturing method, which, based on the additive manufacturing equipment provided in the foregoing embodiments, includes the following steps: Step 100: Heat and melt the metal inside the cylinder 10 to a liquid state and maintain the temperature of the liquid metal 20 within a preset temperature range; Step 200: Control the electromagnetic induction coil 60 to keep the liquid metal 20 in a heated and convection state under the electromagnetic force of the electromagnetic induction coil 60; Step 300: The printing material 421 is sprayed onto the support plate 31 on the lifting platform 30, and the printing material 421 is deposited layer by layer by the high-energy beam heat source 411 to form the printed workpiece 100. The lifting platform 30 is controlled to move closer to the bottom of the cylinder 10 and move down, and the formed part of the printed workpiece 100 is immersed in the liquid metal 20. Step 400: After printing is completed, the printed workpiece 100 is completely immersed in the liquid metal 20 for in-situ heat treatment. Step 500: Cool the temperature of the liquid metal 20 to slightly above the melting point temperature of the liquid metal 20, and adjust the cooling rate as needed by at least one of the heating component 50, the electromagnetic induction coil 60, the insulation layer 91 and the cooling component 92; Step 600: Control the lifting platform 30 to move upward until the upper surface of the lifting platform 30 is exposed outside the liquid metal 20.

[0049] In this embodiment, the liquid metal 20 is heated to a molten state by the heating component 50 and controlled to be in a flowing state by the electromagnetic induction coil 60. The liquid metal 20 in a flowing state can be provided in the cylinder 10 for heating the printed workpiece 100. The liquid metal 20 in a flowing state can uniformly heat the formed part of the printed workpiece 100, avoiding uneven temperature field distribution of the liquid metal 20 during the process.

[0050] In some embodiments, the minimum value of the preset temperature range in step 100 may be greater than the melting point of the liquid metal 20. In some examples, the preset temperature range is -19°C to 700°C.

[0051] In some embodiments, the flow rate of the liquid metal 20 in step 200 can be flexibly adjusted by controlling the magnitude of the current supplied to the electromagnetic induction coil 60, and no specific limitation is made.

[0052] In some embodiments, step 300 specifically includes: Step 310: Control the surface of the support plate 31 on the lifting platform 30 to be flush with or slightly lower than the liquid surface of the liquid metal 20; Step 320: Control the jetting assembly 40 to a preset position so that the printing material 421, the high-energy beam heat source 411 and the support plate 31 are in contact. The printing material 421 is loaded into the material delivery structure 42. The printing environment is sealed and filled with an inert gas (e.g., argon). When the oxygen content of the printing environment is lower than 100ppm, the printing material 421 is supplied to the high-energy beam heat source 411 through the material delivery structure 42 for single-layer deposition in the molten pool formed on the support plate 31. After the printing height reaches about 1cm, the lifting platform 30 is controlled to descend. The descending height of the lifting platform 30 is consistent with the single-layer deposition height of the additive manufacturing equipment. After the lifting platform 30 has descended, the next single-layer deposition continues. As the printing height gradually increases, the formed part of the printed workpiece 100 is gradually immersed in the liquid metal 20.

[0053] In this embodiment, the initial height of the lifting platform 30 is made level with the liquid surface of the liquid metal 20, and the height of each descent of the lifting platform 30 is consistent with the single-layer deposition height. With this setting, the formed part of the printed workpiece 100 can be immersed in the liquid metal 20 as much as possible, so that the different heights of the formed part of the printed workpiece 100 are heated evenly.

[0054] In some embodiments, the single-layer deposition height can be 0.01~4 mm. In one example, the single-layer deposition height can be 0.35 mm.

[0055] In some embodiments, the step 400 of completely immersing the printed workpiece 100 that has been printed into the liquid metal 20 for in-situ heat treatment specifically includes: after printing is completed, completely immersing the printed workpiece 100 that has been printed into the liquid metal 20, and keeping the temperature of the liquid metal 20 higher than the phase transition temperature or ductile-brittle transition temperature of the printed workpiece 100 for a preset time.

[0056] In this embodiment, the printed workpiece 100 that has been printed is subjected to in-situ heat treatment, which can further maintain the uniform heating of each part of the printed workpiece 100. Compared with directly taking out the printed workpiece 100 after printing is completed, this embodiment places the printed workpiece 100 that has been printed in liquid metal 20 for heat treatment. The cooling rate is slower, which can avoid the deformation or cracking of the printed workpiece 100 caused by rapid cooling during the heat treatment and transfer process.

[0057] In some embodiments, the preset duration of in-situ heat treatment is 1 to 1000 hours, depending on the material of the printed workpiece 100, and is not specifically limited here.

[0058] In some embodiments, the temperature range of in-situ heat treatment can be 25~1200°C. In some embodiments, in-situ heat treatment can be immersing the printed workpiece 100 in liquid metal 20 while maintaining a constant temperature, or heating the liquid metal 20 to raise the temperature around the printed workpiece 100 to a relatively high level.

[0059] In some embodiments, the liquid metal 20 is gradually cooled in step 500. This can be done by gradually cooling it at room temperature without any treatment, or by using the cooling component 92 to accelerate the cooling efficiency.

[0060] In some embodiments, after step 600, the method further includes: under inert gas protection, slowly cooling the printed workpiece 100 to room temperature primarily through thermal radiation and limited axial heat conduction at a rate of 0.5°C to 2°C per minute. The printed workpiece 100 is then removed after cooling to room temperature.

[0061] In some embodiments, the printed workpiece 100 may be made of a metal-based material, composite material, polymer material, ceramic, etc. In some examples, the printed workpiece 100 may be made of Ti6Al4V, 316L, or stainless steel.

[0062] It should be understood that the embodiments described herein should be considered in a descriptive sense only and not for limiting purposes. The description of features or aspects within each embodiment should generally be considered as other similar features or aspects that may be used in other embodiments. Although one or more embodiments have been described with reference to the accompanying drawings, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope defined by the claims and their equivalents.

Claims

1. An additive manufacturing apparatus, characterized in that, include: A cylinder, used to hold liquid metal; A lifting platform is located inside the cylinder; the lifting platform includes a support plate, which can move up and down inside the cylinder. The spraying assembly is located on the side of the support plate of the lifting platform away from the bottom of the cylinder. It is used to spray printing material onto the support plate of the lifting platform and use a high-energy beam heat source to deposit the printing material layer by layer to form a printed workpiece. The formed part of the printed workpiece can be driven by the lifting platform to be immersed in the liquid metal. A heating assembly, located on at least one side of the cylinder, is used to heat liquid metal; An electromagnetic induction coil is arranged around the side wall of the cylinder and is used to heat and drive the flow of the liquid metal when energized.

2. The additive manufacturing equipment according to claim 1, characterized in that, There is a gap between the electromagnetic induction coil and the side wall of the cylinder; And / or, the support plate includes a first support plate and a second support plate located on the side of the first support plate away from the bottom of the cylinder body, the second support plate being detachably connected to the first support plate.

3. The additive manufacturing equipment according to claim 1, characterized in that, The heating assembly includes a first heating assembly, which is arranged around the side wall of the cylinder body in a direction from the bottom of the cylinder body to the top of the cylinder body. The first heating assembly and the electromagnetic induction coil are arranged alternately around the side wall of the cylinder body.

4. The additive manufacturing equipment according to claim 1, characterized in that, The additive manufacturing equipment also includes a temperature detection element and a controller. The controller is electrically connected to the temperature detection element and the heating assembly. The temperature detection element is used to detect the temperature of the liquid metal. The controller is used to collect the temperature detected by the temperature detection element and control the heating assembly to stop heating or maintain the target temperature when the temperature of the liquid metal reaches the target temperature.

5. The additive manufacturing equipment according to claim 4, characterized in that, The temperature detection element includes a first temperature detection element, which is disposed on the inner wall of the cylinder and in contact with the liquid metal. And / or, the temperature sensing element includes a second temperature sensing element, the lifting platform includes a lifting shaft connected to the support plate, the lifting shaft has a hollow cavity, and the second temperature sensing element is located in the hollow cavity and in contact with the support plate.

6. The additive manufacturing equipment according to claim 1, characterized in that, The additive manufacturing equipment also includes a heat insulation layer, which is disposed on the side of the heating component away from the cylinder.

7. The additive manufacturing equipment according to claim 1, characterized in that, The additive manufacturing equipment also includes a cooling assembly located on the outer surface of the cylinder and in contact with the cylinder.

8. The additive manufacturing equipment according to claim 7, characterized in that, The heating assembly further includes a second heating assembly. The second heating assembly and the cooling assembly are both located on the bottom wall of the cylinder away from the lifting platform, and the second heating assembly and the cooling assembly are arranged alternately.

9. An additive manufacturing method, characterized in that, Based on the additive manufacturing equipment as described in any one of claims 1 to 8, the additive manufacturing method includes: The metal inside the cylinder is heated and melted into a liquid state, and the temperature of the liquid metal is maintained within a preset temperature range; The electromagnetic induction coil is controlled to keep the liquid metal in a heated and convection state under the electromagnetic force of the coil. The printing material is sprayed onto the support plate of the lifting platform, and the printing material is deposited layer by layer to form a printed workpiece through a high-energy beam heat source. The lifting platform is controlled to move closer to the bottom of the cylinder and move down, and the formed part of the printed workpiece is immersed in the liquid metal. After printing is completed, the printed workpiece is completely immersed in liquid metal for in-situ heat treatment. The temperature of the liquid metal is cooled to slightly above the melting point of the liquid metal, and the cooling rate is adjusted as needed by at least one of the heating components, electromagnetic induction coils, insulation layers and cooling components; The control lift is moved up until the upper surface of the lift is exposed outside the liquid metal.

10. The additive manufacturing method according to claim 9, characterized in that, The step of immersing the printed workpiece completely in liquid metal for in-situ heat treatment after printing is completed includes: immersing the printed workpiece completely in liquid metal after printing is completed, and keeping the temperature of the liquid metal higher than the phase transition temperature or ductile-brittle transition temperature of the printing material for a preset time.

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